When David Valmont walked out of a movie theater in New York after a screening of "Snow White and the Huntsman" last summer, he did not feel it had been worth his while. So he walked into another theater in the same complex and caught "Prometheus" for free.

It's something he does once or twice a year, he said. "Especially if the first movie was bad I'd want to wash the taste out of my mouth," the 29-year-old freelance graphic designer explained.

Theater hopping is an old art, fueled by the rise of the modern multiplex. While it is often attributed to bored or rebellious teenagers, a surprising number of people across the country continue to do it well into adulthood.

To some it is a guilty pleasure. To others, it is a way to counter the rising expense of going to the movies. And to theater owners, it is a cost of doing business and a minor inconvenience.

"It's a terrible habit I learned from my mother, who still does it to this day," Valmont said, laughing. "She'll go and see two or three movies at a time. Her philosophy is ‘I'm just a nice old lady. No one's going to stop me.'"

Ryan Noonan, a spokesman for AMC Theaters, which is the second-largest chain in the United States, said that staff are trained to make sure that all moviegoers get to the appropriate auditorium.

"While we can't provide security tactics publicly, we keep our eyes open and maintain a keen sense of awareness, without being intrusive to moviegoers," he said.

But experts point out that most theater chains have little incentive to crack down. Theater hoppers probably represent less than half a percent of lost business, as compared to video piracy, which could represent 10 to 20 percent, said Chad Beynon, a theater, gaming and leisure senior analyst at Macquarie Securities in New York.

And if many seats in the theater are unfilled anyway, it's not adding to the movie house's expenses.

"It costs the same amount to clean the theater, to show a movie, so there's no incremental cost for that person sitting in the seat," Beynon said.

Most theater hoppers cite high ticket prices as their main motivation. In 2011, the average price of a movie ticket in the United States was $7.93, according to the National Association of Theatre Owners, and it has been rising steadily for years. In New York, one adult ticket for an evening 3D movie can leave your wallet $18 lighter.

Prices are high

"The prices for movie tickets alone are high," said Jesus Salgado, 27, a maintenance worker, who has theater hopped in Queens, N.Y. "Add to that the high price of drinks and food and you feel like you've been robbed. You want to make up for that."

Sometimes, it is just about what movies are showing and whether the timing is right. "My husband and I don't really have the same taste in movies, so sometimes I'll go to one and he'll go to another, and then he'll go to a different one and I'll go to another," said C. C., a 64-year-old legal administrator who would only give her initials because she still theater hops and did not want her name associated with it.

Mostly in large theaters

Not surprisingly, theater hopping tends to happen more often in larger theaters. Smaller movie houses are usually laid out on one floor so anyone trying to move from one auditorium to another can be more easily seen, said Shanise Evans, a manager at a single-story Regal Entertainment theater in Colorado.

However, during her time as an employee in a downtown Denver multiplex, Evans saw theater hoppers more frequently. "That's where there are more people trying to get more for their dollar," she said.

Sometimes she would see regulars who came every day. "They'd buy a ticket for the first show of the day and be there all day," Evans recalled.

One preventive measure used by some theaters is having separate entrances and exits for each auditorium.

Sherlene Chatterji, 22, a student at Stanford University, said she had been to a theater in Palo Alto, Calif., where the exits led out of the complex entirely and staff would watch patrons to make sure that they left after a show.

C.C., the legal administrator, said she had also observed movie theaters getting better at timing shows to discourage people moving from one to another. "They'll set the times so you can't catch the beginning of the next movie or you'll have to wait forever and are seen loitering," she said.

Enforcement unlikely

Sometimes when there is a popular show and every seat in the theater has been sold, the staff will check tickets to weed out theater hoppers.

But it is unlikely that movie theater operators will enforce stricter measures anytime soon.

"You only need a few people to run the property," said Beynon, the industry analyst. "That's one of the beauties of the business. I don't think they're going to do anything to add to the costs like hire more people" to prevent hopping.

So do theater hoppers have any qualms about their misdeeds?

"'No' is the honest answer," said Valmont, the graphic designer. "I remember when tickets were $5. The movie I'm about to see tonight is $18, and on a Tuesday night that's a lot of dollars."